Data transmission by light via polymer fibers and optical wireless LAN offers the automobile industry new opportunities.
If you are travelling in an autonomous car you will have plenty of time to use the media. While the driver is engrossed in a book, his front-seat passenger may be reading the news on her tablet. But the reading light doesn’t come from a lamp and the wireless LAN doesn’t come from a hotspot. The car’s roof liner provides both – the light and the connectivity – via polymer optical fibers, POF for short.
POF as an alternative to glass fiber
Like glass fiber, polymer fiber consists of a transparent core through which the data runs – except that it is made of plastic and not glass. Plastic sheathing provides protection and shielding. These so-called plastic optical fibers have many positive properties. POF cables are very thin, for example, with a diameter of about two millimetres, yet robust and significantly more flexible than glass fiber. They can be laid flexibly around the interior of a car. They also withstand the heat and vibration of an engine compartment and can connect the vehicle technology there.
More users, more data, less energy?
The precious frequency range available for conventional wireless transmission may in future no longer be sufficient.
Other uses for polymer optical fiber
- As an addition to or replacement for WLAN in a home network
- As side-radiating fibers to illuminate Plexiglas displays or signage
- As a transmission line for so-called sollectors to conduct sunlight into rooms
- As a transmission line for light in general to separate the light source from the location to be illuminated
- As a sensor fiber for simple strain, pressure or brightness measurement
- As a rotary transmitter for transmitting optical signals from a stationary to rotary axis such as for motors or in robotics
POF cables also conduct no electrical current, generate no radiation and cannot be influenced by electromagnetic fields, so they can be laid unproblematically alongside 230-volt cables in cable ducts. Installation and connection are easy. Expensive special tools like those required to splice glass fiber are not needed. Polymer fibers do, however, have a higher attenuation than glass fibers, which has a negative influence on data throughput over longer distances. But high transmission rates can be achieved over short distances such as wiring in vehicles. Research scientists at Nuremberg University of Technology’s POF Application Centre
have already achieved data rates of several megabits per second.
Questions to Prof. Christian-Alexander Bunge (Part 1)
Why did you decide to do research on polymer fibres of all things?
Data and light for the vehicle interior
Polymer fibers have been in use in the automotive sector since the 1990s. The MOST (Media Oriented Systems Transport) bus, for example, is a serial field bus system with POF cables that automobile manufacturers all over the world use to transmit audio, video, voice and data signals in cars. Impervious to electromagnetic interference, POF cables are predestined for use in electric cars and their battery systems. Polymer fibers can also be used to make luminous textiles or - if the fibers are prepared locally - to make structures and contours of any kind luminous. So why not combine the two?
Intensive research on polymer fibers is under way at the University of Telecommunications in Leipzig (HfTL). The POF textiles developed at the HfTL Institute of Communications Technology, for example, can be stretched across the roof liner of a car. With these flexible fibers the research scientists then illuminate not only the entire interior of the vehicle but also specific points, such as for use as reading lights. This special material even provides Internet access. The light can be so modulated as to convert the roof liner into an optical wireless LAN hotspot. In-car mobile devices can then go online via the roof liner.
Questions to Prof. Christian-Alexander Bunge (Part 2)
Why not simply provide in-car Internet access via a WLAN hotspot?
Optical WLAN from the lamp
The Leipzig research scientists’ optical solution transmits light and data together – both wired and wireless. Optical data transmission solutions of this kind are also a speciality of the Fraunhofer Heinrich Hertz Institute (HHI). Visible Light Communication (VLC)
via the lighting in rooms is appropriate inter alia where conventional wireless communication could interfere with sensitive systems, such as at hospitals or on board planes.
Other uses for optical WLAN
- At hospitals data connection via the light in the operating theater can be used to transmit X-ray images to the operating theater or to control an operating theater robot
- On board a plane the light of the ceiling lamp can be used to provide all passengers with Internet access or stream films on their tablets
- At trade fairs the stand lighting can relay the exhibitor’s information to the mobile devices of stand visitors
- Optical WLAN is an alternative wherever multiple light sources are available, as in open-plan offices, classrooms and conference rooms
For optical WLAN special lamps are connected to the Internet via landline or powerline, providing a data connection via their LED lamps with an electrical component switching the diode quickly on and off. Where the human eye no longer notices any flickering, the photodiode in the laptop or smartphone reads information from the modulated light signal. The result is a so-called Light Fidelity network
, or Li-Fi for short.
Optical WLAN could also be used in a connected car scenario. Much as in buildings the infrastructure is already in place. It is the street lamps. Upgraded to incorporate data-transmitting LEDs, they could serve as hotspots for passing vehicles. The only precondition is that there must be a line of sight between the two.